Storing audio-centered information with a multi-level table-of contents (TOC) mechanism having redundant sub-TOCS

ABSTRACT

Audio-centered information is stored on a unitary medium by using a Table-of-Contents (TOC) mechanism that specifies an actual configuration of various audio items on the medium. In particular, each one of a set of one or more Track Areas gets at least two mutually logically conforming Sub-TOCs assigned. This allows to retrieve any constituent Sub-TOC part from at least any correct copy of the Sub-TOCs. Furthermore, one or more Master-TOCs are provided for specifically pointing to each of the Sub-TOCs.

BACKGROUND OF THE INVENTION

[0001] The invention relates to a method as recited in the preamble ofclaim 1. Storing digital audio on unitary media such as disc or tape iswidespread. In case of actual sub-division of the audio into multiplesub-items, providing a Table-of-Contents (TOC) allows to access theinformation in an easy manner. Such TOC will specify at least what hasbeen stored and where it has been stored. The audio may be definedaccording to various standardized audio formats, such as two-channelstereo, multiple (5-6) channel audio such as in surround soundapplications, and possibly others. An audio provider may wish to combinevarious track areas having the same and/or different such formats on asingle medium such as an optical disc.

SUMMARY TO THE INVENTION

[0002] In consequence, amongst other things, it is an object of thepresent invention to allow an audio management system to allow a user toaccess various audio track areas in a fast and easy manner. NowTherefore, according to one of its aspects the invention ischaracterized according to the characterizing part of claim 1. A user isnow able to distinguish between various track areas and to navigateamong the various items of a single track area in a robust manner, andif possible, without encumbrance through data users in the TOC itself.

[0003] The invention also relates to a unitary storage medium producedby the method, to a storing device arranged for practising such method,and to a reader or player device arranged for interfacing to suchstorage medium. A particular audio medium instance could be restrictedto storing only stereo, so that the multi-channel version wouldeffectively be a dummy. For reasons of standardizing, the multilevel TOCmechanism will then also be adopted. Further advantageous aspects of theinvention are recited in dependent claims.

BRIEF DESCRIPTION OF THE DRAWING

[0004] These and further aspects and advantages of the invention will bediscussed more in detail hereinafter with reference to the disclosure ofpreferred embodiments, and in particular with reference to the appendedFigures that show:

[0005]FIGS. 1a, 1 b a record carrier,

[0006]FIG. 2 a playback device,

[0007]FIG. 3 a recording device,

[0008]FIG. 4 a file system for use with the invention;

[0009]FIG. 5 a storage arrangement for the invention;

[0010]FIG. 6 a structure of an audio area.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0011]FIG. 1a shows a disc-shaped record carrier 11 with track 19 andcentral hole 10. Track 19 has a spiral pattern of turns formingsubstantially parallel tracks on an information layer. The carrier maybe an optical disc with a recordable or prerecorded information layer.CD-R, CD-RW and DVD-RAM are recordable discs. Audio CD is a prerecordeddisc. Prerecorded discs may be manufactured by first recording a masterdisc and then pressing consumer discs. Track 19 on a recordable recordcarrier may be formed by a preembossed track structure. The track may beconfigured as pregroove 14 to allow a read/write head to follow thetrack 19 during scanning. The information is recorded on the informationlayer by optically detectable marks along the track, e.g. pits andlands.

[0012]FIG. 1b is a cross-section along the line b-b of a recordablerecord carrier 11, wherein transparent substrate 15 caries recordinglayer 16 and protective layer 17. Pregroove 14 may be implemented as anindentation, an elevation, or as a material property deviating from itssurroundings.

[0013] For user convenience, the audio information on the record carrieris subdivided into items, which may have a duration of a few minutese.g. songs in an album or movements of a symphony. The carrier will alsocontain access information to identify the items, such as a Table OfContents (TOC) or a file system like ISO 9660 for CD-ROM. The accessinformation may include playing time and start address for each item,and further information like a song title.

[0014] The audio information is recorded in digital representation afteranalog to digital (A/D) conversion. Examples of A/D conversion are PCM16-bit per sample at 44.1 kdz known from CD audio and 1 bit Sigma Deltamodulation at a high oversampling rate e.g. 64×Fs called Bitstream. Thelatter is a high quality encoding method, allowing either high qualitydecoding or low quality decoding. Reference is had to the publications‘A digital decimating filter for analog-to-digital conversion of hi-fiaudio signals’, by J. J. van der Kam, document D5 infra, and ‘A higherorder topology for interpolative modulators for oversampling A/Dconverters’, by Kirk C. H. Chao et al, document D6. After A/Dconversion, digital audio may be compressed to variable bitrate audiodata for recording on the information layer. The compressed audio datais read from the carrier at such speed that after decompressionsubstantially the original timescale will be restored when continuouslyreproducing the audio. Hence the compressed data must be retrieved fromthe record carter at a speed dependent on the varying bitrate. The datais retrieved at so-called transfer speed, i e. the speed of transferringdata bytes from the record carrier to a decompressor. Providing therecord carrier with constant spatial data density gives the highest datastorage capacity per unit of area. The transfer speed is proportional tothe relative linear speed between the medium and the read/write head.With buffer before the de-compressor, actual transfer speed is the speedbefore that buffer.

[0015]FIG. 2 shows a playback apparatus according to the invention forreading a record carrier 11 of the type shown in FIG. 1. The device hasdrive means 21 for rotating carrier 11 and read head 22 for scanning therecord track, Positioning means effect 25 coarse radial positioning ofread head 22. The read head comprises a known optical system with aradiation source for generating beam 24 that is guided through opticalelements and focused to spot 23 on an information track. The read headfurther comprises a focusing actuator for moving the focus of theradiation 24 along the optical axis of the beam and a tracking actuatorfor fine positioning of spot 23 in a radial direction on the centre ofthe track. The tracking actuator may comprise coils for moving anoptical element or may be arranged for changing the angle of areflecting element. The radiation reflected by the information layer isdetected by a known detector in the read head 22, e.g. a four-quadrantdiode, to generate a read signal and further detector signals includingtracking error and focusing error signals for the tracking and focusingactuators, respectively. The read signal is processed by standardreading means 27 to retrieve the data, for example through a channeldecoder and an error corrector. The retrieved data is sent to dataselection means 28, to select the compressed audio data for feeding tobuffer 29, The selection is based on data type indicators also presenton the carrier, e.g. headers in a framed format. From buffer 29, thecompressed audio data go to de-compressor 31 as signal 30. Decompressor31 decodes the compressed audio data to reproduce the original audioinformation on output 32. The de-compressor may be fitted in astand-alone audio D/A convertor 33, or the buffer may be positionedbefore the data selection. Buffer 29 may reside separately or may becombined with a buffer in the decompressor. The device furthermore has acontrol unit 20 for receiving control commands from a user or from ahost computer not shown, that via control lines 26 is connected to drivemeans 21, positioning means 25, reading means 27 and data selectionmeans 28, and possibly also to buffer 29 for filling level control. Totis end, the control unit 20 may comprise digital control circuitry, forperforming the procedures described below.

[0016] The art of audio compression and decompression is known. Audiomay be compressed after digitizing by analyzing the correlation in thesignal. and producing parameters for fragments of a specified size.During de-compression the inverse process reconstructs the originalsignal. If the original digitized signal is reconstructed exactly, the(de-)compression is lossless. Lossy (de) -compression will not reproducesome details of the original signal which will be substantiallyundetectable by the human ear or eye, Most known systems for audio andvideo, such as or MPEG, use lossy compression, whereas losslesscompression is used for computer data. Examples of audio compression anddecompression are given in D2, D3 and D4 hereinafter,

[0017] Data selection means 28 will retrieve from the read data certaincontrol information, in particular indicating the transfer speedprofile. The data selection means 28 will also discard any stuffingdata, that had been added during recording according to the speedprofile. When the control unit 20 is commanded to reproduce an audioitem from the record carrier, positioning means 25 will position thereading head on the portion of the track containing the TOC. Thestarting address and the speed profile for that item will then beretrieved from the TOC via the data selection means 28. Alternatively,the contents of the TOC may be read only once and stored in a memorywhen the disc is inserted in the apparatus. For reproducing an item,drive means 21 will rotate the record carrier at the speed indicated bythe speed profile. The required rotation rate may be given as such inthe speed profile for setting the drive means, Alternatively the speedprofile may comprise a bitrate, and then the rotation rate can becalculated as follows. The radial position of the item can be calculatedfrom the starting address, because the record carrier density parameterslike track pitch and bit length, will be known to the playback device,usually from a standard. Subsequently the rotation rate can be derivedfrom the bitrate and the radial position. To provide continuousreproduction without buffer underflow or overflow the transfer speed iscoupled to the reproduction speed of the D/A converter, i.e. to thebit-rate after decompression. Thereto the apparatus may comprise areference frequency source for controlling the decompressor and therotation rate may be set in dependence on the reference frequency andthe speed profile, The rotation rate may also be adjusted by the averagefilling level of the buffer 29, e.g. lowering rotation rate when thebuffer is more than 50% full on average.

[0018]FIG. 3 shows a recording device for writing information on a(re)writable record carrier 11. During a writing operation, marksrepresenting the information are formed on the record carrier. The marksmay be in optically readable form, e.g. as areas whose reflectiondiffers from their surroundings, by recording in materials such as dye,alloy or phase change, or in the form of areas with a direct ofmagnetization different from their surroundings. Writing and reading ofinformation for recording on optical disks and usable rules forformatting, error correcting and channel coding, are well-known, e.g.from the CD system. Marks may be formed through a spot 23 generated onthe recording layer via a beam 24 of electromagnetic radiation, usuallyfrom a laser diode. The recording device comprises similar basicelements as described with reference to FIG. 2, i.e. a control unit 20,drive means 21 and positioning means 25, but it has a distinctive writehead 39. Audio information is presented on the input of compressionmeans 35. Suitable compression has been described in D2, D3 and D4. Thevariable bitrate compressed audio on the output of compression means 35is sent to buffer 36. From buffer 36 the data is sent to datacombination means 37 for adding stuffing data and further control data.The total data stream is sent to writing means 38 for recording. Writehead 39 is coupled to the writing means 38, which comprise for example aformatter, an error encoder and a channel modulator. The data presentedto the input of writing means 38 is distributed over logical andphysical sectors according to formatting and encoding rules andconverted into a write signal for write head 39. Unit 20 controls buffer36, data combination means 37 and writing means 38 via control lines 26and perform the positioning procedure as described above for the readingapparatus. The recording apparatus may also have the features of aplayback apparatus and a combined write/read head.

[0019]FIG. 4 shows a file system for use with the invention, for whichvarious different options are feasible. The inventors have proposed thatthe storage medium should be based on a UDF file system or on an ISO9660 file system, both of which systems are standard to a skilled artperson. In the alternative case, no file system should be present at alland the relevant sector spaces should be kept empty.

[0020] In the file system, all audio will be stored in Audio Fileslocated in SubDirectory SCD_AUDIO. As shown in FIG. 4, the hierarchy isbased on ROOT file 50 that points to various subaltern files 52, 54, 56.The structure of MASTER.TOC 52, here single, will be discussedhereinafter. Further, there is a 2_CH_AUDIO file 54, This points to TOC2_CH_TOC 58 and also to the various stereo tracks TRACKn.2CH 60,Furthermore, M_CH_AUDIO file 56 points to TOC M_CH_TOC 62 and inparallel therewith to the various multi-channel tracks TRACKn.MCH 64.

[0021]FIG. 5 shows a first storage arrangement for use with theinvention, which by way of example has been mapped on a single serialtrack. Along the horizontal axis the following items are evident. Item120 is a Lead-in area that is used for mutually synchronizing the readerand the driving of de medium. Item 122 represents the File Systemdisclosed with reference to FIG. 4. Item 124 represents a MASTER_TOCthat may be configured according to standard procedures and pertains tosubsequent items Stereo AREA 126 and Multi-channel AREA 128, and ifnecessary also to Extra Data AREA 130. The lengths of these three areasneed not be standardized, inasmuch as various different amounts ofinformation may be present. With respect to the audio areas, the audiotrack areas proper, as well as the associated SUB₁₃TOCs are included.Apart from the disclosure hereinafter, the contents of items 126, 128,130 may be defined according to conventional standards that bythemselves do not constitute part of the invention. Generally, the twoaudio areas may have the same structure and contain the same kinds ofinformation, apart from distinguishing between the various channels. Theaudio may be plan coded or loss-less coded. All kinds of audio may bemultiplexed with supplementary data, such as Compact Disc Text.

[0022] Item 132 represents a Lead-Out Information. The latter item isused in particular during search operations. Its tracks do not containinformation further than track numbers and addresses. The number oflead-out tracks may cover a ring of some 0.5 to 1 millimeter wide.According to the above, the stored information may either be accessedvia the file system as laid down in item 122, or via the TOC structurelaid down in item 124, and more particular, via a two- or multi-levelTOC structure to be discussed hereinafter.

[0023] Any of the single or plural Master TOCs 124 will begin at arespective uniformly standardized offset position from the start of theLead-in area, such as at byte number 500 for the first Master TOC. Inthe embodiment a Master-TOC measures only one standard-size sector andprimarily contains pointers to the various Sub-TOCs or Area-TOCs to bedisclosed hereinafter. A preferred syntax of a Master-TOC is as follows:

[0024] 1. A 16-byte Signature identifies the Master-TOC, such as by“SACD Master TOC”, the signature containing three space characters, butthe apostrophes not being part of the definition.

[0025] 2. A 2-byte Spec_version indicates the version number of theformat used in the disc.

[0026] 3. A 14-byte Space has been reserved, such as for alignmentstaffing,

[0027] 4.A 4-byte integer 2CH-start_address contains the logical addressof the first sector of the , stereo area.

[0028] 5. A 4-byte integer 2CH-end_address contains the logical addressof the last sector of the stereo are&

[0029] 6. A 4-byte integer MC-start_address contains the logical addressof the first sector of the Multi channel area

[0030] 7. A 4-byte integer MC-end_address contains the logical addressof the last sector of the Multi channel area.

[0031] 8. A 4-byte integer Extra_data_start_address contains the logicaladdress of the first sector of the Extra Data area.

[0032] 9. A 4-byte integer Extra_data_end_address contains the logicaladdress of te last sector of the Extra Data area.

[0033] The total information pertaining to the above is 56 bytes.Further features may be added to a Master-TOC. If a certain area, suchas the stereo area, the Multi channel area, or the Extra Data area isnot present, both start and end addresses of the area in question havevalue zero.

[0034] Next, items 126 and 128 will contain Sub-TOCS or Area-Tocs forthe Stereo and Multi-Channel Audio intervals, respectively, formatted aswill be disclosed hereinafter with respect to FIG. 6. A preferred syntaxof a Sub-TOC is as follows:

[0035] 1. A 16-byte Signature identifies the Sub-TOC in question such asby “SACD stereo TOC” for a stereo audio area and “SACD MC TOC” for aMulti Channel audio area, the number of bytes being attained by addingtrailing space characters

[0036] 2. A 2-byte Spec_version indicates the version number of theformat used in the disc.

[0037] 3. A 4-byte Sub_TOC_length indicates the number of bytes presentin the actual TOC.

[0038] 4. A 10-byte Space has been reserved, such as for alignmentstuffing.

[0039] 5. A variable size set of /* Disc Parameters */ may be present,such as a Name of an Album( ) and a Name of a Catalogue( ).

[0040] 6. A 4-byte disc_play_time indicates the total linear playingtime of the disc expressed as a time code.

[0041] 7. A 4-byte disc_name_pointer indicates the offset in bytes fromthe start of the Sub_TOC in question to the start of the disc_name( )field. If the value in question is 0, this indicates that the disc_name() field is absent.

[0042] 8. A 4-byte disc_date_pointer indicates the offset in bytes fromthe start of the Sub_TOC in question to the start of the disc_date( )field. If the value in question is 0, this indicates that the disc_date() field is absent.

[0043] 9. A 4-byte disc_copyright_pointer indicates the offset in bytesfrom the start of the Sub_TOC in question to the start of thedisc_copyright( ) field. If the value in question is 0, this indicatesthat the disc-copyright( ) field is absent.

[0044] 10. A 4-byte disc_publisher_pointer indicates the offset in bytesfrom the start of the Sub_TOC in question to the start of thedisc_publisher( ) field. If the value in question is 0, this indicatesthat the disc_publisher( ) field is absent.

[0045] 11. A variable size Track_List( ) may be present for each one ofa plurality of audio tracks to contain an offset information withreference to the start of the TOC in question, plus various furtheritems, such as the name of track and any of a great multiplicity ofitems that are presumably interesting to a listener of the recording inquestion.

[0046]FIG. 6 shows an exemplary structure of an audio area 126, 128 inFIG. 5. Here, the track area is preceded by Area or Sub-TOC-1 andsucceeded by Area TOC-2. These are two identical copies. Another mannerof logical conformance may be produced by bit-wise inversion. Anyway,each copy taken separately must contain all information contained in thetwo TOCs. The locations thereof are for each separate Area TOC given ina higher level Master TOC. A gap between the Track Area and succeedingArea TOC-2 is not allowed, On the other hand, a gap between precedingArea TOC-1 and the Track Area is allowed, symbolized by area G, Such gapwill generally not contain significant information, in particular, noother TOC or track. Therefore, logically the tack area will abut at bothends to the TOCS. Due to the doubling of the Area TOCs and their mutualdistance, any interference therewith through environmental or otherinfluences will usually not be doubled for the two copies. Inconsequence, the probability for correct storage of all parts of theArea TOO in at least one of the two versions thereof will be practicallyguaranteed, even without the providing of internal redundancy. Errorcorrecting through such redundancy would often cost an unjustifieddelay. In fact, if the preceding TOC is correct, the starting of a trackmay be effected virtually immediately.

[0047] List of related documents:

[0048] (D1) Research Disclosure number 36411, August 1994, p. 412-413

[0049] (D2) PCT/IB97/01156 (PHN 16.452) 1 bit ADC and losslesscompression of audio.

[0050] (D3) PCT/IB97/01303 (PHN 16.405), Audio compressor.

[0051] (D4) EP-A 402,973 (PHN 13.241), Audio compression.

[0052] (D5) ‘A digital decimating filter for analog-to-digitalconversion of hi-fi audio signals’ by J. J. van der Kam in PhilipsTechn. Rev. 42, no, 67, April 1986, pp. 230-8.

[0053] (D6) ‘A higher order topology for interpolative modulators foroversampling A/D converters’, by Kirk C. H. Chao et al in IEEE Trans. onCircuits and Systems, Vol 37, no. 3, March 1990, pp. 309-18.

1. A method for storing audio-centered information on a unitary storagemedium while using a Table-of-Contents (TOC) mechanism for thereinspecifying an actual configuration of various audio items on saidmedium, being characterized by assigning at least two mutually logicallyconforming Sub-TOCs to each one of a set of one or more Track Areas,thereby allowing retrieving any constituent Sub-TOC part from at leastany correct copy of said Sub-TOCs, and furthermore providing at leastone Master-TOC for specifically pointing to each of said Sub-TOCs.
 2. Amethod as claimed in claim 1, wherein said Sub-TOCs abut at mutuallyopposite ends to their associated Track Area.
 3. A method as claimed inclaim 1, wherein the number of sub-TOCs per Track Area is exactly
 2. 4.A method as claimed in claim 1, and furthermore providing any Master-TOCat a standard offset location with respect to an initial location ofsaid medium.
 5. A unitary medium produced by practising a method asclaimed in claim
 1. 6, A medium as claimed in claim 5 and executed as anoptically readable disc.
 7. A reader device for interfacing to a mediumas claimed in claim
 5. 8. A device as claimed in claim 7, and beingprovided with disc hold means, optical read means nd disc drive meansfor living a disc tack along said optical read means.
 9. A storingdevice being arranged for practising a method as claimed in claim 1.